Use the Halt Transaction tool.  This is where you permanently stop a transaction. You will not be able to recover data from any documents referencing this transaction between the buyer and seller. All non-transaction specific files and progress will be saved. Only use this function if you want to permanently cease all actions with the other party.

Another buyer can be invited to continue the sell of the business. The system saves all of your documents that don't pertain directly to the cancelled transaction.